Remote control system for automatic positioning of switches



R. L. SAMSON REMOTE CONTROL SYSTEM FOR AUTOMATIC Sept. 16; 19582,852,728

POSITIONING OF SWITCHES 3 Sheets-Sheet 1 Filed Aug. 28, 1956 m5 ATTORNEYSept. 16, 1958 R. L. SAMSON REMOTE CONTROL SYSTEM FOR AUTOMATICPOSITIONING OF SWITCHES 3 Sheets-Sheet 2 Filed Aug. 28, 1956HMHHHHHHHHHHMHHHHWMMHMUH J 3E T .IQ w: l QM H mm T 37, T u I I &\Q\ anmw I u am I 92 $4 n Ab\ Q EN mm x: 82 E a ix? I 3 sn n. SE hu mMw w: AVv h mm SIN I I \E an A Q $8 I V NM k m: 0 m n m 1 Q Q l 5 x NE M I nmiIa mm w 5 llllllll ll 1| m N q 32 H 3: r IIL I I I I I I I I I I I I l II I l I I I I I I I I I I I I I l l I I I I I I I I I I l I I I L N m mR N mm R N D M w L v PA w E A H ,R w I IIIIIIIIIIII III EQI Q? N MGNQA dS 39 BMW Sept. 16, 1958 R. L. SAMSON REMOTE CONTROL SYSTEM FOR AUTOMATICPOSITIONING OF SWITCHES Filed Aug. 28, 1956 5 Sheets-Sheet 3 Avqrvl wonINVEN'I'OR. RAL PH L. SAMEIDN HIE: ATTDRNEY United Stats REMOTE CONTROLSYSTEM FOR AUTOMATHC POSITIONING @F SWITCHES Ralph L. Samson, Wycltofl',N. l, assignor to Curtiss' Wright Corporation, a corporation of DelawareApplication. August 28, 1956, Serial No. 606,6?6

27 Claims. (Cl. 318-467) This invention relates to switching circuitsand more particularly to a control system for automatic positioning of anumber of switches remotely located from one another. I

A system of the afore-described character is known in the art andcomprises two auxiliary switching circuits for each of the controlledswitches positioned in accordance therewith. A number of control wiresinterconnect the auxiliary switching circuits which together with theinterconnecting wires form part of an energization circuit for a relay.The arrangement is such that an energization current for said relayflows only when the switches are in non-corresponding positions.Actuation of the relay closes an energization circuit for a rotarysolenoid or other suitable sequential positioning means, which indiscrete steps positions one of the controlled switches through itspositions to eventually reestablish correspondence of positions of thetwo switches.

The necessity of two auxiliary circuits per controlled switch and thenecessity of large diameter wire to carry the heavy relay currentresults in rather bulky equipment, which in certain applications,-forexample in aircraft or aircraft trainers, is objectionable because ofthe small available space. In other applications use of the devicedescribed has been disadvantageous when it became necessary to integrateadditional controlled switches in an already existing system. Upon suchoccasion it had been necessary to interrupt service between the alreadyoperating stations containing position-controlled switches prior toinstallation of an additional station, or at least it was necessary forthe installer of the new station to be informed of the position of theswitches in already operating stations. Bilateral operation, to be morefully defined hereinafter, has also proved difficult with the systemdescribed.

It is an object of the invention to provide a control system including aminimum of auxiliary control switching circuits, utilized at theirhighest efiiciency, requiring a minimum of space and a low current drainthus permitting the use of small diameter wires.

Another object of the invention is to provide a control system of thecharacter described which admits of ready integration of new controlledswitches without disruption of service of the previously installedswitches, any newly installed switches aligning themselves automaticallytherewith.

Still another object of the invention is to provide a control system ofthe character described suitable for complete bilateral operation.

These and other objects will become more readily apparent from thefollowing description when considered together with the accompanyingdrawings, in which:

Fig. 1 is a block diagram of the control system,

Fig. 2 is a diagrammatic view of the control system including in greaterdetail the control circuitry within block BB of Fig. 1,

Fig. 3 is a diagrammatic view of a number of auxiliary switching circuitpatterns, the configurations of which 2,852,728 Patented Sept. 16, 1955depend upon the number of positions of the controlled switches, and

Pig. 4 is a partly diagrammatic and partly perspective view of apparatusfor bilateral control.

In the drawings like characters generally identify like parts. 1

According to the invention a control circuit is provided having threeterminals for energization thereof by a pair of alternating voltagesapplied from each end terminal to the center terminal. A number ofnetworks are connected across the end terminals, which number dependsupon the number of positions of the controlled switches. Each network.is provided with three taps or junction points, the innermost junctionpoint being arranged to be normally at the potential of the center inputterminal. Each of the junction points intermediate of one end terminaland an innermost junction point. is respectively connected by a control'lead to the terminals of an auxiliary switching circuit which isoperable according to the operation of a controlled switch. Each of theremaining outer junction points is connected by a control lead to asimilar auxiliary switching circuit of another controlled switch. Thecommon terminals of the auxiliary switching circuits are connected tothe center input terminal. As a controlled switch and therefore itsassociated auxiliary switching circuit traverses the possible switchpositions, distinct of the associated junction points areshort-circuited to the center input terminals, whereas the remainingjunction points are not so short-circuited. The arrangement is such thatwhen the switches are in corresponding positions the outer junctionpoints of each circuit are either both shortcircuited or both notshort-circuited to the center input terminal. Consequently in suchnormal condition the innermost junction points remain at the potentialof the center input terminal. When the switches are in noncorrespondingpositions at least one outer junction point is not in the same circuitcondition as the other outer junction point of the same network.Consequently, the innermost junction point of such network is no longerat the potential of the center input terminal, so that a rectifiedcurrent may flow through a diode connected to the innermost junctionpoint of such one circuit. Each network is provided with a diodeconnected to its innermost junction point and the rectified current ofat least one such diode is sufiicient to actuate a means forsequentially positioning one or more of the switches and theirassociated auxiliary switching circuits to ultimately reestablishcorrespondence of switch positions.

The invention will be more fully set forth in the subsequentdescription, in which the controlled switches are described by way ofexample as intended for selector tuning of similar radio receivers ofthe type used in aircraft or aircraft trainers for example, but it is tobe understood that the invention is applicable to switchable apparatusin general, whether mechanically, electromechanically, or electronicallyswitchable. Accordingly the terms switch and position are intended toapply to mechanical, electromechanical, or electronic switching means.

Referring to Fig. 1, reference character A identifies a master stationand reference characters B, C, D, etc., identify a number of slavestations. The stations may contain, for example, similar selector switchtunedradio receivers. Tuning of the master station is accomplished byexternal manual or external automatic rotation of the selector switch a,which switch may be rotatable in either direction. Switch 100a comprisesa main switch ing wafer or circuit or section 101a which has a number ofdiscrete positions corresponding to the completion of a circuit betweenthe rotatable common or permanent or sesame collector contact 102a andone of the stationary angularly equispaced selector contacts 1a, 2a, 3aetc. (The sequential numbering 1, 2, 3 etc., thus represents a selectorcontact as well as a switch position for an assumed counter-clockwisedirection of rotation beginning with the condition of collector contact162 in contact with the selector contact 1a as indicated.) Suitabledetents (not shown) are provided to preclude the possibility of thecollector contact 102 coming to rest in a position intermediate ofselector contacts. The collector contact 102 is connected to anassociated lead 102a which runs to an appropriate circuit, whereas eachof the selector contacts 1a, 2a, 3a, etc. is respectively connected toassociated outgoing leads 1a, 2a, 311, etc., in turn leading toappropriate circuits. The slave stations contain corresponding switcheslttlllb, 1000, 100d, etc. and respectively associated main wafers 101b,1010, 101d, etc., each switch having the same number of switch positionsas the switch 100a as signified by the correspondence of the referencenumerals for the switch components and associated leads. It is desiredthat whenever the tuning frequency of the master station is changed byswitching of the collector contact 102a the slave stations be tuned tothe master station frequency by internal automatic setting of thecollector contacts 102b, 1020, 102d, etc. to their respective selectorcontacts corresponding to the selector contact to which the collector102a has been set.

To this end an auxiliary control switch wafer 103a is ganged to the mainswitch 101a as indicated by the connections 10411. As a matter ofconvenience in illustration separate wafers are indicated for the mainwafer 101a and the auxiliary wafer 103a, but it is to be understood thatthe two sets of stator contacts could be disposed on the two faces of asingle stator disc or even on the same face. However, only one auxiliarycontrol switching circuit is required and herein lies one of theadvantages of the present invention. Prior art devices had required twoauxiliary control switching circuits. The auxiliary control wafer 103ahas as many switch positions as the main wafer 101a. By way of exampleand for reasons which will be apparent from the description hereinafter,the number of positions of the main and auxiliary wafers is assumed tobe an exact power of two and for this reason the last position of themain switch 100a is indicated by the reference character 2W1. Theauxiliary wafer 103a comprises a rotatable common or permanent orcollector contact 105a which is permanently grounded as diagrammaticallyindicated by the slip ring and brush connection 1060:, the brush portionof which is tied to ground. The collector contact 105a is provided witha number of radially projecting contact portions 105:11, 105x12, 105a3,105ml, 105515, ltlSafi, liGSa'Y, and ltl5a8, which in their rotarytravel come in contact with selector contacts. Corresponding to theselector terminals 1, 2, 3 n of the main wafer lltlla there are provideda series of stationary angularly equispaced selector contactssequentially designated as 11a, 12a, Ina, to which there arerespectively connected a series of outgoing control leads ll, 11, lln.Whenever a contact of the series 11a, 12a, 112a connects to one of theprojecting contact portions such contact is grounded.

As shown in Fig. 1 only the contact 11a is connected to a projectingportion (105111) and therefore is the only grounded selector contact.The leading edge 105011 of the projecting portion 105x11 is slightlyahead of the contact 11a (considered in the assumed counter-clockwisedirection of rotation). Such position of the leading edge 105x11slightly in advance of the contact lllla is intended to signify that themain and auxiliary wafers ltllla and 103a are in switch position 1;similarly, the fact that the leading edge 105611 advances to a positionslightly ahead of the contacts 2a, 3a, etc., is intended to indicaterespec- 3. tively switch positions 2, 3, etc., in addition to indicationof a grounded circuit condition.

The leads 11, 12, 1n are connected respectively to the terminals 21b,22b, 2111) in the slave station B; to the corresponding terminals 21c,22c, 2 nc in slave station C; to the corresponding terminals 21d, 22d,2nd in the slave station D, etc. Additionally in the slave station E theleads 11, 12, in are connected respectively to the ends of similarresistors, 31, E52, 3n, whose other ends are connected together and arealso connected to an end 107 of a secondary 108 of a transformer 159,whose primary 110 is energized by the alternating voltage V The centertap 111 of the secondary 168 is grounded, whereas a line 112 isconnected to the other end 113 of the secondary 108. A series'ofterminals 114b, 114e, 114d, etc., respectively within the slave stationsB, C, D, etc., are connected to the line 112 and therefore to the end113 of the secondary 103. The slave stations C, D, etc., also containgrounded circuit points connected to a ground wire (not shown)interconnecting all the stations.

The remainder of the control circuitry for the slave station E iscontained within the block BB and is illustrated in greater detail inFig. 2. The remaining slave stations contain circuitry functionallyidentical to the circuitry within the block BB and for this reason nofurther illustration is required and therefore not presented.

For Fig. 2 it is assumed that the number n is 3, i. e. that the switch ahas eight positions; correspondingly the auxiliary Wafer 103ais providedwith three selector contacts 11a, 12a and 13a.

The main and auxiliary wafers 101a and 103a are in the switch position 1as indicated by the connection of collector contact 102a to the selectorcontact 1a and by reason of the leading edge :21 being slightly ahead ofthe selector contact 11a. Positioning of said leading edge 105mlslightly ahead of contacts 12a or 13a would signify that the switches101a and 103a are in switch position 2 or 3 respectively, in addition toindication of a grounded circuit condition. Positioning of the leadingedge 105a1 slightly ahead of the broken lines 14a, 15a, 16a, 17a or 13aon the other hand would merely signify that the main and auxiliary waferare respectively in the fourth, fifth, sixth, seventh or eighthpositions. In Fig. 2 the collector contact 105a has merely two radiallyprojecting contact portions 105ml and 105112, the span and spacing ofwhich will be explained hereinafter.

From each of the terminals 21b, 22b, and 23b (and in the case of n otherthan three from each of the contacts up to and including Znb) thereextends a circuit to the terminal 114b, all such circuits being similar.In particular the circuit extending from the terminal 21b includes aresistor 41 one of Whose ends is connected to the terminal 21b and whoseother end is connected to the junction point 51. A resistor 41',substantially of the same value as resistor 41, is connected between thejunction points 51 and 61, and a resistor 31]), substantially of thesame value as resistor 31b, is connected between the junction 61 and theterminal 114b. The equal resistors 31b and 31b may be of relatively lowvalue, say of the order of thousands of ohms, whereas the equalresistors 41 and 41' may be of the order of 100,000 ohms or higher. Theresistors 31b and 31b and the corresponding similar resistors 32b and32b, 33b and 33b serve to preclude short-circuiting of the ends 197 or113 of the secondary 108 in the event that the leads 11, 12, 13 or thecorresponding leads 11', 12, or 1.3 are grounded and also to decouplethe circuits from one another. In the case of more than one slavestation the resistors 31b, 32b, 33b, etc., and corresponding resistors31c, 32c, 330, etc., additionally serve to decouple the respective slavestation control circuits from the common end 113 of the secondary 108.

Analogously there is connected to the terminal 221; an end of a resistor42 similar to resistor 41. The other end of resistor 42 is connected tothe junction 52 from which a resistor 42', substantially of the samevalue as resistor 42, extends, the other end of resistor 42', beingconnected to the junction 62. A resistor 32b, substantially of the samevalue as resistor 32b, is connected between the junction 62 and theterminal 114b. In similar fashion a resistor 43, similar to theresistors 41 and 42, is connected between the terminal 23b and thejunction 53, and resistor 43', substantially of the same value asresistor 43, is connected between the junction 53 and 63. A resistor33b, substantially of the same value as resistor 33b, is connectedbetween the junction 63 and the terminal 11%. More generally for itother than three there will be n similar circuits connected between theterminals 21b, 22b, Znb each containing a resistor similar to theresistor 41 connected between the terminal corresponding to 211: and thejunction corresponding to 51, a resistor corresponding to 41 andconnected between the junctions corresponding to 51 and 61 substantiallyof the same value as resistor 41, and a resistor corresponding to 31b,substantially of the same value as resistor 31b and connected betweenthe junction corresponding to 61 and the terminal 114k. Ganged to thecommon shaft of the main switch water 1011) is an auxiliary wafer 1133bwhich is of a construction functionally identical to the construction ofthe auxiliary wafer 103a. The auxiliary wafer 103b has appropriate partsidentified in the same manner as have corresponding parts of theauxiliary wafer 103a with the letter b replacing the letter a of acorresponding part. A line 11 extends from junction 61 to the contact11b and similarly lines 12' and 13' connect junction 62 to contact 12band junction 63 to contact 13b respectively. More generally, for 11other than three, lines similiar to line 11 will be connected from ajunction corresponding to 61 to a contact corresponding to 11b. Thus itis seen that n balanced circuits are connected across the terminals 107and 113.

As shown in Fig. 2 the contact 11a and its corresponding contact 1112are grounded whereas the contacts 12a and 13a and the correspondingcontacts 12b and 1312 are not grounded. The currents which flow over theline 11 through contact 11a to ground and over line 11' through contact11b to ground are relatively low, of the order of a few milliamperes, ascontrasted to the heavy relay currents drawn by devices previously knownover corresponding lines and contacts. The same low current value holdstrue for each of the remaining control lines were it grounded throughits associated contact. Thus a small wire size is permissible for thelines 11, 12 and 13 (and for that matter, for the lines 11, 12, and 13,as well). Moreover, as has been pointed out before, the construction ofthe auxiliary wafer 103a is of the highest simplicity, and as will bepointed out hereinafter, is of the greatest efficiency of utilization.These aforegoing advantages combine to permit construction of the masterstation switching circuitry in a very small space as compared to thecircuitry included in devices constructed in accordance with prior art.

The junction 51 is at ground potential by reason of the grounding of thecontacts 11a and 11b, whereas the junctions 52 and 53 are also at groundpotential but for a difierent reason, namely because the circuitsconnected across the ends 107 and 113 of the secondary 108 are balancedwith respect to the ground and junctions 52 and 53 respectively. Anumber of unidirectional devices or diodes 71, '72, 73 have theircathodes respectively connected to the junction points 51, 52, 53'. Theanodes of these diodes are connected together at junction 115 to whichis also connected a rectifier load circuit comprising the parallelconnected resistor 116 and capacitor 117 whose other ends are grounded.The diodes serve as rectifying means in the forward direction and alsoas means for decoupling their associated circuits from one another, inview of their blocking capability in the reverse direction. Alsoconnected to the junction 115 is the grid 118 of a triode 119 whosecathode 12b is grounded and whose anode 121 is connected through thecoil 122 of a relay 123 to the positive terminal of a direct voltagesource 13+, the negative terminal thereof being grounded. The triode 119is normally conducting; in fact by reason of the direct cathode returnto ground the triode is saturated, so that a steady anode current flowsthrough relay coil 122 thereby positioning the relay armature 124 in theposition in contact with the terminal x as indicated by the solid arrow124. The triode 119 is in fact saturated since none of the diodes 71,'72, '73 are conducting, their anodes being at ground potential suppliedthrough the resistor 116 whereas their cathodes are also at groundpotential supplied through the resistor pairs 41 and 41, i2 and 42, and43 and 43', derived from terminal pairs 211'; and 61, 22b and 62, 23band 63 respectively, as explainetl hereinabove. In the event of cut-oilof the triode 119 its anode current would cease to flow and consequentlythe armature 124 would be released to contact terminal y and assume thealternate position indicated by the broken line 124 arrow therebyclosing a circuit 125. Circuit 125 extends from a terminal 125a suppliedby the voltage source V to the contact y, via the relay armature 124,via the line 126 to a terminal 127 of a rotary solenoid 128, through thestator winding of solenoid 122i, thence to the other terminal 129 ofsaid rotary solenoid, and via the line 131) to the other terminal 125bsupplied by the source V. When the circuit 125 is closed the rotarysolenoid 1.23 is energized and its rotor, which is unidirectionallyrotatable (herein counter-clockwise), is rotated in discrete steps; i.e. the rotor will rotate through a fraction of one revolution, come to astop temporarily, rotate through an equal fraction of a revolution, cometo another step momentarily, etc. Rotary solenoids are Wellknown in theart and are manufactured, for example, hy the Oak Manufacturing Companyunder the trademark Ledex. In particular the rotary solenoid 128 isarranged to complete one revolution in eight steps corresponding to theeight switch positions of the switch wafers 101a, 103a, 10115, and 103b,the rotor also being ganged to the shaft 10%. The arrangement is suchthat as the rotor of the solenoid 128 advances by A3 of a revolutionfrom the position indicated the wafers 161!) and 11 212 will assumeswitch position 2; similarly upon completion of an additional revolutionthe wafers 1111b and 1&3]; will assume switch position 3, etc.

The operation of the triode 119 is essentially of a bistable nature inthat Within wide limits, determined by the minimum current required foractuation of relay 123, it is only of circuit significance that saidtriode 119 be either conducting to an extent suflicient to actuate therelay or insufiicient for actuation. Therefore, it is not necessary thatthe halves of the transformer secondary 103 be accurately balanced, noris it necessary that the mates of the resistor pairs 31b and 31b, 32band 32b, 33b and 33b, or the mates of the resistor pairs 41 and 41', 42and 42', 43 and 43', or even the characteristics of the diodes 71, 72,73 be closely matched, for the most unfavorable condition to beencountered is that of a slight unbalance current being drawn throughone or more of said diodes, resulting in a negative bias of the grid113, which negative bias however is insufificient to reduce the anodecurrent to a magnitude sufficient to actuate relay 123.

To facilitate understanding of the operation of the ap paratus, let itbe assumed that the operator at the master station A manually changesthe positions of the wafers 101a and 103a from the indicated position 1to the position 2 whether by counter-clockwise or clock-wise rotation.The contact 114: and therefore the terminal 21b and junction 51 will beat ground potential as in the previous switch position 1 owing to thegrounding by the collector a. Similarly the contact 13a and thereforethe terminal 23b will retain their previous ungrounded circuitcondition. Tie contact 12511, which in the first 5 switch position hadnot been grounded, is grounded in the second switch position since theprojecting portion 105ml will now also be connected to contact 12a. Onthe other hand junction 62 is still at its previous potential,substantially equal to the potential of end 113 of the secondary 168.Consequently an unbalanced circuit condition exists as between junction62 and terminal 22b and junction 52 is no longer at ground potential,resulting in a flow of rectified current through the diode 72, and anegative bias is developed across resistor 1116 thereby cutting-oil? thetriode 119. Triode anode current ceases to flow, releasing armature 124to connect to terminal y thereby actuating the rotary solenoid 128 whichin a first step rotates counter-clockwise through /8 of a revolutionthereby advancing the wafers 10117 and 1(l3b to the position 2.Considering the wafer 1035 in the position 2 it is apparent that theselector contact 12b will now be grounded through the collector contact1051) thereby changing the potential at junction 62 to ground potential,establishing balanced ground potentials at terminals 2% and 62,terminating the flow of rectified current through the diode 72 andrestoring Zero bias to the grid 113. Once more the triode 119 is throwninto conduction, reverting contact 124 to the left-hand position andopening the energizing circuit 125 of the rotary solenoid 123, whichtherefore will advance no more and consequently leave the wafers 161b,lltifib in a position 2 matching the position 2 of wafers itiia and103a, so that slave station B is tuned to the same frequency as ismaster station A.

In order to achieve such operation it is necessary that the timeconstant of the rectifier load comprising resistor 116 and capacitor 117be less than the response time of the relay 123 including the timerequired for the armature 124 to shift from the position x to theposition y or vice versa. if the converse were the case, the contact 124would stay in one or the other positions longer than desired, therebypermitting the rotor of solenoid 128 to advance beyond the desiredposition. The resistor 116 should be large enough so that conduction ofmerely one diode is sufiicient to develop triode cut-otf bias acrosssaid resistor 116.

From the aforegoing it is apparent that the operation of the apparatusis governed by the binary nature of operation of the selector contacts11a, 12a, etc., and 11b, 1211, etc., in that such contacts may be eithergrounded or not grounded. So long as a selector contact such as 11a isgrounded and its mate such as11b is also grounded, the pointscorresponding to 21b and 61 are balanced and no current flows throughthe associated diode such as '71 capable of activating the rotarysolenoid 128. The same considerations hold true in the event that acontact such as 1111 is not grounded while its mate such as 111)likewise is not grounded. So long as each of the contacts 11a, 12a, 13ais in the same circuit condition as its mate 11b, 12b, 13b respectively,the rotary solenoid 128 is not activated. In the event that at least onecontact such as 11a is not in the same condition as its mate such as 11b(i. e. one grounded and the other not grounded) an unbalance conditionis established as between the points corresponding to 2112 and 61causing a current to flow through the associated diode corresponding to71 thereby cutting off the triode 1-19 with a consequent actuation ofthe rotary solenoid 128. Thereafter the solenoid 128 will remain activeto rotate the collectors 102b and ltlSb through as many steps as arerequired to reestablish balance as between the mates of each pair ofterminals 21b and 61, 22b and 62, 23b and 63 so that ultimately none ofthe diodes will conduct, whence once more triode 119 is thrown intoconduction and the rotary solenoid 128 is deactivated.

Because of the aforesaid binary nature of operation of the contacts 11aetc. it is possible to construct the collector 105a (and for that matterits mate 1051;) in such a manner that in one switch position of thewafer 103a all three contacts 11a, 12a, 13a will be grounded, in

' respect to the other.

another switch position none of the contacts 11a, 12a and 13;; will begrounded, in three distinct positions only one of these contacts will begrounded (namely only contact 11a in one position, only 12a in anotherposition, and only 13a in the third position), and in three otherdistinct positions only such contacts as constitute the possiblecombinations of two contacts at a time will be grounded whereas thethird will not (i. e. in one position the contacts 11a and 120 will begrounded, in another position the contacts 12a and 13a will be grounded,and in the third position contacts 11a and 1311 will be grounded). Thetotal number of distinct positions thus is eight so that with n equal tothree, only three selector contacts 11a, 12a, and 13a and associatedlines 11, 12:, and 13 are required. More generally for a main waferlllla having 2 positions it is possible to arrange the collector 195a sothat with h associated selector contacts in one switching position allof the n contacts are grounded, in one switching position none of the tcontacts are grounded, and in a number of distinct positions suchcontacts as constitute the possible combinations of l, 2, 3 (n-l)contacts at a time, are grounded. The total number of all of theaforementioned combinations (including the positions wherein all of thecontacts are grounded at one time and none of the contacts are groundedat one time) can be shown mathematically to be equal to-2 thereforemerely :1 control selector contacts and therefore n associated controlleads are required of the auxiliary wafer 163:; (or 1133b) for 2switching positions, as contrasted to n+1 selector contacts inaccordance with apparatus heretofore known. A switching schedule orprogram for an eight position switch (11:3) is shown in Table I, whereinthe letter Y signifies that the pertinent selector contact is grounded,whereas the letter N indicates that the pertinent selector contact isnot grounded.

Table I Selector Contact Switch Position Y N N Y Y N Y Y Y N Y Y Y N Y NY N N N Y N N N Table I is applicable to both auxiliary wafers 103a and1031;. 7

From an examination of Table I it is apparent that if the switch a is inany one of the eight positions whereas the switch 100]) is in any otherof the remaining seven positions there is at least one non-identity ofcontact condition as between one of the mates of the pairs 11a and 11b,12a and 12b, and 13a and 13b with In such case at least one of thediodes 71, 72 and 73 will be rendered conductive thereby activating therotary solenoid 128 which will rotate the wafers llllband 19312 indiscrete sequential steps. So long as in any of these steps non-identityof condition of at least one contact terminal of the group 11a, 12a, and13a exists with respect to the condition of the mates 11b, 12b, and 131;respectively, the rotary solenoid 128 will continue to advance throughas many more steps as are required to establish identity of conditionof'each contact with respect to the condition of its con tact mate;

The construction of the collector contact a (or 105b) can be determinedat once by reference/to the column in Table I appearing under selectorcontact 11.

Thus it is noted that in switch positions 1, 2, and 3 selector contact11 is grounded requiring the projecting portion 105a1 capable ofgrounding three consecutive selector contacts. In switch position 1portion 105111 spans the arcuate space between contact Ho and brokenline 17a protruding slightly beyond each. In switch position 4 theletter N signifies that selector contact 11 is not grounded requiring anabsence of a projecting portion adjacent to the broken line 16a. In theposition 5 the letter Y appears for selector contact 11 not followed bythe letter Y in position 6, therefore requiring the elevated portion105x12 capable of grounding only one contact at a time. In switchposition 1 portion 105(12 lies adjacent to the broken line a. The letterN appears for each of the positions 6, 7, and 8, requiring the absenceof any projecting portion adjacent to the broken line 14a and thecontacts 13a and 12a.

It can be shown that for an eight-position switch and for an arcuatespacing between contacts ill and 12 of /a revolution and an equalarcuate spacing between contacts 12 and 13 the functional constructionof the collector 195 is unique. Under the same assumed conditions ofequiangular spacing of consecutive selector contacts of the auxiliarywafer at intervals of of a revolution, only one functional collectorconstruction is possible for the cases of 12:1 or 11:2. 011 the otherhand for 11 greater than three and with increasing n, more and morepossible functional constructions for the collector 105 become possible.

Thus for a l6-position switch (11:4) the switching schedules or programsshown in Tables ll, ill, TV and V can be derived, wherein the selectorcontacts are numbered sequentially as 2%, 292, 203, and 25194.

Table IV Selector Contact Switch Position Y N N N Y Y N N Y Y Y N Y Y YY 10 N Y Y Y 6 N N Y Y Y N N Y N Y N N Y N Y N t Y Y N Y N Y Y N Y N Y YN Y N Y N N Y N N N N Y N N N N Table V Selector Contact Switch PositionY N N N Y Y N N j Y Y Y N Y Y Y Y N Y Y Y Y N Y Y N Y N Y N N Y N Y N NY N Y N N Y N Y N Y Y N Y N Y Y N N N Y Y N N N Y N N N N Thecorresponding functionally only possible auxiliary wafer collectorconstructions are shown in respectively Selector Contact Switch PositionTable III Selector Contact zzzzzaz22mzazzazezmzzamzmem zzzzezzzaezezz zz:zeezzamzeeemz 222azzzeezezzezazeezzemzwaaezz zzezzz mz+42.z izaz mzzeaszmeeem zK:22maz :zzezazmzzmezameezzzz Subject to the assumptionsindicated before, functionally ll only one auxiliary collectorconstruction is possible for each of the cases of a four-position switch(11:2) and a two-position switch (11:1) which are respectively shown inFig. 3e and Fig. 3 The switching schedules from which Fig. 3e and Fig. 3are derived are respectively presented in Tables VII and VIII.

So far only such switching arrangements have been considered as have anumber of positions equal toan exact power of 2. In Fig. 3g and Fig. 3bthere are shown two possible auxiliary control water collector patternsfor a three-position switch derived from the following Tables IX and Xrespectively.

Table IX Selector Contact Switch Position Y N N Y N N Table X SelectorContact Switch Position Two selector contacts 201 and 202 are requiredin the case of a three-position switch as were also required in the caseof a four-position switch. However in Table IX the possible combinationcorresponding to switch position 2 in Table VII is not availed of,whereas in Table X the possible combination corresponding to switchposition 4 in Table VII is not availed of. In general where the numberof switch positions is not an exact power of two, as many auxiliarywafer selector contacts and associated leads will be required as arerequired of the jswitch having a number of positions equal to the nexthighest exact power of two. In that sense a switch having a number ofpositions not equal to an exact power of 2 will require an auxiliarycontrol wafer which is not utilized more efiiciently.

The number of selector contacts, leads, and associated control circuitsmaybe expressed so as to cover multiposition switches in general,Whether the number of positions is or is not an exact power of two. Fora switch having a number of positions 2"|p, the required number ofcontrol circuits is n+1, where n is any positive integer (including andp is also a positive integer satisfying the relation 16 1512". As theswitch traverses the 2 +p positions, such contacts as constitute 2"+p ofthe possible 12 2 combinations of (n+1), n, (n l)l, 0 contacts at a timeare grounded.

As stated before, if additional slave stations C, D, etc., are required,it is merely necessary to duplicate the circuitry shown within the blockBB in said additional stations C, D, etc. Alternatively in accordancewith another form of the invention, the relay 123 is provided with anumber of additional armatures similar to 124 equal to the number ofadditional slave stations desired, which additional armatures 124 in theposition y complete energization circuits similar to 125. Suchener'gization circuits are connected to the common source V forenergizing additional rotary solenoids in each additional slave station,said additional solenoids corresponding to the rotary solenoid 128 andbeing ganged to respectively the connections 1040, 104d, etc. In suchcase all other corresponding circuitry in said additional stations areomitted.

However the duplication of the entire circuitry within block BB in eachof the additional slave stations is advantageous if it is desired tointroduce additional slave stations with the master and at least oneslave station already in operation without necessity to interrupt theirservice and without necessity to notify the installer of the switchposition of the existing master and slave stations. Thus if originallyonly stations A and B had been installed and were in operation, theinstaller of the slave station C to be introduced would merely berequired to connect leads from the terminals 21c, 22c, Znc and from theterminal 114; to respectively the lines 11, i2, 1n and 112 and aninterconnecting ground wire, and thereafter turn on the power in thestation C, whence the switch 101?: would align itself automatically withthe master station switch 101a.

Many modifications of the basic apparatus are possible. For example, therelation of the collector contact and the selector contacts may beinverted, i. e. the former may be made stationary and the latterrotatable. It is also possible to invert the position of each of thediodes '71, 72, 7n, and accordingly normally bias the triode 119 tobelow cut-off instead of to saturation and connect the terminal xinstead of the terminal y to the source V. The advantage of thisalternative arrangement lies in the fact that no anode current is drawnby the triode .119 except when necessary to align a slave station withthe master station A. However, the arrangement hereinbefore describedand illustrated in Fig. 2 possesses the advantage that in the event offailure of the voltage B+ the rotary solenoid 128 operates continuously,thereby indicating such failure.

The previously described operation of the apparatus has been essentiallyone-way or unilateral in that the master station switching operation isperformed externally manually or externally automatically whereas theslave station switching operations are performed internally art--tomatically. In certain instances it may be desirable to provide two-wayor bilateral operation; i. e. whenever the tuning at any one station(whether heretofore designated as master or slave station) is changed,it is desired to automatically retune the remaining stationsaccordingly. To this end the master station could be provided with thecomplete apparatus shown in the block BB in Fig. 2 and the connections104a, 104b, 104e, etc., arranged for external manual or externalautomatic as well as internal automatic actuation. However, in such caseit would be necessary to arrange the detents associated with theseconnections to assure merely unidirectional (herein counter-clockwise)rotation, as otherwise an attempted exter nal clockwise rotation in aparticular station would be opposed by an attempted counter-clockwiseinternal actuation in the same station. Alternatively one could providesuitable reversing switch means for bidirectional operation of therotary solenoids as typified by 128, connected to suitable circuit meansfor sensing at remote stations the direction of manual rotation of thelocal station sesame so as to rotate each solenoid in the same directionas the externally actuated switch. Whichever of the aforegoingalternatives is adopted, difficulty in the form of a runaway conditionmay still be encountered in the event that the external switching isperformed at a high speed compared to the rate of solenoid rotation. Insuch instance, it is possible that the solenoid in the local station,whose switch position has been changed rather rapidly due to externaloperation, is still subject to the local internal automatic actuation,in which case the local rotary solenoid would continue to change thelocal switch position and all other remote solenoids would do likewise.Moreover, since no switch is now at a permanent position all switcheswould rotate continuously and not come to a stop, not knowing to whichother switch position to align themselves.

Accordingly there is shown in Fig. 4 a form of the invention suitablefor two-way or bilateral operation which includes means for precludingthe aforementioned run-away condition and also admits of externaloperation in either direction. In Fig. 4 the number of switch positionsis limited to four and merely station E is illustrated in detail, itbeing understood that station A and any additionally desired stations C,D, etc., contain apparatus functionally identical to that shown withinthe block BB.

Referring to Fig. 4 the connections 104k include a rotatable shaft 302to which is keyed for rotation therewith a spur gear 304 which mesheswith an idler pinion 305, which in turn meshes with another spur gear366, which is keyed to a rotatable shaft 308 for rotation therewith. Amanually operable selector knob 310 is keyed to the end of the shaft308, so that when an operator changes the local station tuning manuallyby rotation of the knob 310, such operation rotates shaft 303 and gear3%, which through the idler 305 in turn drives the gear 304 and theshaft 332 to effect the desired tuning change. The idler pinion 305 isprovided for maintaining the assumed counter-clockwise direction ofrotation as the normal direction, solely as a matter of convenience inthe description. It could be dispensed with, in which case the gear 3&6would be arranged to mesh directly with the gear 364. The knob 310 isprovided with a dial pointer 311 to indicate the selected frequency on adial (not shown). The end of the shaft 302 is connected to the shaft 312of the rotary solenoid 128 by means of a friction drive arrangementgenerally indicated as 313 and described in detail hereinafter.

A single-pole double-throw momentary push-button switch 314 is securedto the side of the knob 310 so that as the operator manually rotates theknob 310 he also actuates the switch 314. Said switch 314 is indicatedschematically at 314'. It comprises a common terminal 316 and twoselector terminals 318 and 320. Normally, i. e. in the absence of manualactuation, the switch is in the position bridging contacts 316 and 318as indicated by the solid arrow 321. Upon manual actuation contacts 316and 320 are bridged as indicated by the broken-line arrow 321. Thecontacts 316 and 318 are included in the line 322 connecting terminal125a and terminal y in circuit 125, and in the normally bridged positionpermit possible energization of the rotary solenoid 128 in response to achange in switch position at a remote station. Upon actuation of theswitch 314, however, the energization circuit 125 for the rotarysolenoid 128 is broken and local energization is thereby precluded. Toinsure that the energization circuit 125 shall remain disabled for apredetermined time however quickly the push-button switch 314 isreleased, additional holding circuit means provided. To this end a line323 extends from the terminal 125a supplied by the voltage source V tothe common contact 324 of a relay 326 the armature of which is normally(i. e. in the absence of actuation of the switch 314) in the positionindicated by the solid arrow 323. One end of the coil 330 of the relay326 is connected to the terminal 320 of switch 314' and its other end isconnected to the other terminal of the voltage source V via the contact332 and line 334. That end of the relay coil 330 which is connected tothe contact 32%, is also connected to a terminal 337 to which thearmature 32% connects in the event of energization of the coil 33% toassume the alternate position indicated by the associated broken linearrow 328'.

Upon actuation of the switch 314 the connection 316-318 is broken aspreviously indicated to preclude energization of the rotary solenoid128, and at the same time the connection 316-32tl is made therebycompleting an energizing circuit for the relay 326. Such actuation marksthe beginning of a preclusion cycle. A current flows from the terminal125a to the terminal 316, through the contact 321, to the terminal 320,through the relay coil 33%, through the contact 332 to the terminal125b. This current energizes the relay coil 330 thereby shifting therelay armature 328 to the alternate position indicated as 328' andcompleting an additional energization circuit for the coil 330. Thisadditional circuit extends from the terminal 125a via the line 323 tothe terminal 324, through the armature 328 to the relay terminal 337,through the coil 330 through the contact 332 to the terminal 125b. Therelay armature is provided with a second section 338 which normallybridges contacts 340 and 342 in the line 322. Upon energization of thecoil 330 however, the armature section 338 is shifted to the positionindicated by the broken line arrow 338' thereby providing a secondbreaking of the line 322 in addition to the breaking occasioned by theactuation of switch 314. Even though the switch 314 be released ratherquickly the additional energization circuit for the relay coil 330 keepssaid coil 33% energized and the associated relay armatures 328 and 338in the positions indicated by respective broken lines to precludeenergization of the local rotary solenoid 128. Since the preclusion isintended to be only temporary, it is necessary to provide circuit meansfor restoring the armatures 328 and 338 to their normal positions aftersome time delay.

To this end the armature of relay 326 is provided with a third sectionindicated by the solid arrow 344 which normally bridges a commongrounded contact 346 to the contact 3348 thereby normally grounding thegrid 350 of a triode 352 through the line 353 connecting contact 348 togrid 350. The cathode 354 of the triode is connected through a resistor356 to a voltage divider point 358 to which a relatively high positivevoltage is supplied from the positive terminal of the voltage source B+through resistor 360, thence through the resistor 362 to ground, therebynormally biasing the triode 352 considerably below cut-off. The anode364 is connected through the winding 366 of a relay 368 to the positiveterminal of the voltage 8+. The armature associated with the relay 368is in fact the aforementioned contact 332 which normally connects therelay coil 330 via the line 334 to the terminal 12517. Normally no anodecurrent flows through the triode 352 in view of the cut-olf biasprovided. Upon energization of the relay coil 330 however, the armaturesection 344 assumes the alternate position indicated by the broken linearrow 344, thereby opening the short circuit of the grid 350 to ground.Thereafter the voltage at the grid 350 slowly builds up towards thepotential B+ because of the charging of a condenser 370 through thevariable resistor 372, one end of each of which is connected to the grid350 and the other ends of which are respectively connected to ground andto the positive terminal of the voltage 13+. Although the voltage at thegrid 354i is building up, initially no anode current flows as yet untilafter the cut-off voltage has been passed. Thereafter an anode currentflows but is as yet insulficient to energize the relay coil 366 to anextent necessary for actuating its armature 332. Some time thereafter,which time may be regulated by the adjustment of the resistor 372, theanode current passing through coil 366 is sufficient to actuate thearmature 332 and to throw it into the position indicated by the brokenarrow 332', thereby opening the energization circuit for the relay coil33%, reverting the associated armatures 328, 344 and 338 to their normalpositions, once more grounding the grid 35% and rapidly dischargingcapacitor 370, cutting off the triode 352, and reverting the armature332 to its normal position, thus ending the preclusion cycle.

The time constant of the combination of the resistor 372 and capacitor370 may be adjusted, for example, so that the period of a preclusioncycle exceeds the maximum possible time interval during which anoperator is reason ably expected to actuate the switch 314, plus thetime required for one complete revolution of the rotary solenoid 328.Consequently the line 322 must remain open for the maximum possible timerequired of the other solenoids to come to their final position. If atthe end of the cycle the operator were still actuating the switch 314,energization of the local rotary solenoid 128 would, of course, continueto be precluded in view of the breaking of the connections 316-.313. Atthe same time another cycle would begin and the cycles would be repeatedso, long as the operator actuated the switch 314 at the end of a cycleand thus reenergized relay coil, 330.

The arrangement so far described is satisfactory in pre venting therun-away condition, but additionally it may be desirable toprecludemanual actuation of the rotor of the rotary solenoid 128 duringthe period of a preclusion cycle, especially in the event of manualclockwise rotation of the switches and 103b, Where the frictionalopposition torque of the rotor may be sufficiently great to hindermanual operation.

To this end the relay 326. is provided with yet another armature section372 for effecting disconnection of the friction coupling 313. Saidcoupling comprises a disc member 374 which. is rigidly secured to theother end of the shaft 362 for rotation in unison therewith, whereasanother disc member 376 is rigidly secured to the end of a shaft 377 forrotation in unison therewith. A spurgear 373 is keyed to the other endof the shaft 377 for rotation in unison therewith and meshes withanother spur kear 379. which is keyed to the end of the shaft 312forrotation in unison therewith. The gears 378 and 379 are provided formaintaining the assumed counter-clockwise direction of rotation as thenormal direction, solelyas a matter. of convenience in the description.They could be dispensed with, and the disc member 37:? be keyed directlyto the end of the shaft 312.

The disc member 374. may have a larger diameter than the disc member 375to effect a speed reduction through the intervening agency of aconnecting friction disc member 380. Member 389 is normally inengagement with the members 374 and 376 and thereby completes thecoupling connection from the shaft 312 to the shaft 302. Member 380 isrigidly secured to a shaft 381 for rotation in unison therewith. Suchrotation occurs in the case of engagement by the disc member of the discmembers 376 and 374 when the shaft 312 is rotated as a re sult ofswitching at a remote station. Upon such remotely originated rotationthe rotary motion of the shaft 312 is imparted to the gears 31" and 373,to the shaft 377, to the member 371', to member 3%, to member 374, tothe shaft 302 to position the switch 10% ultimately to its requiredposition. The shaft 302 also rotates the gear 384, which through idler325 in turn rotates the gear 3%, the shaft 3.03 and the knob 31th sothat the pointer 311 indicatcs the selected tuning frequency on thedial.

The. shaft 331, in addition to being rotatable within suitable journals332 and 384 is also arranged to axially slidewithiu the bores of saidjournals 352 and 384. Magnetic members 385 and 383 are rigidly securedto the ends of the shaft 381, and the member 38-0 is held in thenormally engaged position owing to the magnetic attrac tion of themember336 by the. electromagnet 390, which comprises a core 392 made ofa magnetic material and a coil 394 wound therearound for carrying amagnetizing current. One end of the coil 394 is grounded whereas theother end is connected via the line 396 to terminal 398 with which thearmature 372 normally makes contact thereby bridging terminal 398 to thecommon terminal 460 which in turn is connected to the positive terminalof a direct voltage source E whose negative terminal is grounded.Normally a magnetizing current flows through the described circuit toenergize the coil 392 and hold the disc member 378 in the engagedposition. Since mere magnetic actuation might result in bounce of themember 378, additional mechanical means are provided to more positivelyassure engagement. Such means comprise one or more angularly spacedlever members 402, one end of each of which is pivotally connected as at404 and towards the other end of which there is provided a recessportion 466, wherein a ball 408 is free to revolve. The ball 408 engagesthe inner surface of the member 386 and is held in engagement throughthe urging of a tension spring 410 connected to the lever 402. The lever492 is also made of a magnetic material, so that both mag netic actionand mechanical action force and keep the member 380 in engagement.

When the relay coil 330 is energized by actuation of the push-buttonswitch 314, the armature 372 is thrown into the alternate positionindicated by the broken line arrow 372' thereby breaking theaforedescribed magnetizing circuit and making another magnetizingcircuit. Owing to the breaking of connection between the terminals 398and 400 the member 386 and the lever 402 are no longer subject tomagnetic attraction by the magnet 390 and therefore are relatively freeto assume an alternate disengaged position, the tension of the spring414) alone being insufficient to maintain the engaged position. When thearmature 372 assumes the alternate position indicated by the broken linearrow 372 another magnetizing circuit is established, extending from thepositive terminal of the voltage E to the terminal 490, to the contact413, over the line 41 to the coil 414 of a similar electromagnet 418 toground. Coil 414' is wound about a similar core member 420. By reason ofsuch magnetization the other magnetic member 388 is attracted to themagnet 418 to positively assure disengagement of the clutch member 380,but its travel is limited by the stops 422 and 424. The magnetic actionis reinforced by mechanical means which comprise one or more similarmagnetic levers 426 pivotally mounted towards one end as at 428 and alsohaving a recess portion 430 wherein a similar ball 432 is free torevolve and engage the member 388. A similar tension spring 434 assurespositive urging of lever 426 towards the member 388 through theintervening agency of the ball 432. When ultimately the relay coil 330is deenergized the armature section 372 resumes the normal positionbridging the terminals 3% and 43%, thereby discontinuing magnetizingcurrent through the coil 416 and reestablishing magnetizing currentthrough the coil 392 and causing once more the engagement of the member38%) with the members 374' and 376. Since the magnetizing current forthe coils 392 and 416 may be rather heavy, capacitors 435 and 438 areconnected respectively across the terminals 4% and 413, and 460 and 398to minimize sparking upon making or breaking of the respective circuits.The remaining circuitry in Pig. 4 is similar to that shown in Fig. 2 andrequires no further discussion. As in the case of one-way operation,additional stations may be readily added. Moreover, because of theabsence of a true master station, some or all of the terminals 114e,114b, etc., may be tied to the end 107 of the transformer secondary 1598instead of solely to the end 1130f this secondary. For this reasonanother interconnecting line 112 is brought out from the end 107 of thesecondary which line 112" is functionally similar to the line 112brought out from the terminal 113 of the secondary.

Thus it will be seen that in the form of invention illustrated in Fig.4, there is provided a bilaterally opassagras erable switch positioningsystem, which includes means for precluding energization of the localinternal automatic positioning means responsive to local externalpositioning, means for continuing such preclusion thereby to prevent arun-away condition, and means for disengaging the local internalautomatic switch positioning means thereby to facilitate externalpositioning, each for a predetermined time substantially equal to theaforementioned. period of preclusion of energization of the localinternal automatic switch positioning means.

it is to be understood that the embodiments described have beenpresented by way of illustration and not by way of limitation, referencebeing had to the appended claims rather than to the aforegoingspecification to determine the scope of the invention.

What is claimed is:

l. A system for maintaining correspondence of positions of a first andsecond switch each having 2 discrete positions, where n is a positiveinteger including zero and p is an integer satisfying the relation 1 p 2comprising in combination means for applying first and second inputvoltages between a point of reference potential and respectively a firstand second input terminal; n+1 control networks connected across saidinput terminals each having a first and second circuit junction pointlocated in balanced circuit. relation to one another relative to saidpoint of reference potential; auxiliary switching means for placing withthe traverse of said first switch at a first of two possible potentialsdistinct 2"+p corn binations of O, 1, 2, n, n+1 of said first circuitjunction points at a time and the remaining of said first junctionpoints at the second possible potential; auxiliary switching means forplacing with the traverse of said second switch at a first of twopossible potentials balanced normally with the aforesaid first potentialrelative to said reference potential the respectively corresponding 2 +pcombinations of O, l, 2, n, n+1 of said second junction points at a timeand the remaining of said second junction points at the second possiblepotential balanced normally with the aforesaid second potential relativeto said reference potential; and means responsive to unbalance ofpotentials of the junction points of at least one of said networks dueto non-correspondence of switch positions for sequentially positioningone of said switches so as to reestablish potential balance of thejunction points of each of said networks and correspondence of switchpositions.

2. A system for maintaining correspondence of positions of an externallypositionable master switch and an internally positionable slave switcheach having 2 discrete positions, where n is a positive integerincluding zero and p is an integer satisfying the relation l'p2comprising in combination means for applying first and second inputvoltages between a point of reference potential and respectively a firstand second input terminal; n+1 control networks connected across saidinput terminals each having a first and second circuit junction pointlocated in balanced relation to one another relative to said point ofreference potential; auxiliary switching means for placing with thetraverse of said master switch at a first of two possible potentialsdistinct 2 +p combinations of 0, l, 2, n, n+1 of said first circuitjunction points at a time and the remaining of said first circuitjunction points at the second possible potential; auxiliary switchingmeans for placing with the traverse of said slave switch at a first oftwo possible potentials balanced normally with the aforesaid firstpotential relative to said reference potential the respectivelycorresponding 2 +p combinations of (l, l, 2, n, n+1 of said secondcircuit junction points and the remaining of said second circuitjunction points at the second possible potential balanced normally withthe aforesaid second potential relative to said reference potential; andmeans responsive to unbalance of potential as between the circuitjunction points of at. least one of said networks due to changed masterswitch position for sequentially positioning saidv switch so as toreestablish potential balance of the junction points of each of saidnetworks and correspondence of switch positions.

3. A system for maintaining correspondence of positions of an externallypositionable master switch and a plurality of internally positionableslave switches, each of said switches having 2"l-p discrete positions,where n is a positive integer including zero and p is an integersatisfying the relation lpS'Z, comprising in combination means forapplying first and second input voltages between a point of referencepotential and respectively a first and second input terminal; first,second n, n+1 control networks connected across said input terminalseach having a first and second circuit junction point located inbalanced relation to one another relative to said point of referencepotential; auxiliary switching means for placing with the traverse ofsaid master switch at a first of two possible potentials distinct 2"+pcombinations of 0, l, 2, n, n+1 of said first circuit junction points ata time and the remaining of said first circuit junction points at thesecond possible potential; auxiliary switching means for placing withthe traverse of one of said slave switches at a first of two possiblepotentials balanced normally with the aforesaid first potential relativeto said reference potential the respectively corresponding 2 +pcombinations of 0, 1, 2, n, n+1 of said second circuit junction pointsat a time and the remaining of said second circuit junction points atthe second possible potential balanced normally with the aforesaidsecond potential relative to said reference potential; and a meansassociated with each of said slave switches responsive to unbalance ofpotential of the circuit junction points of at least one of saidnetworks due to changed master switch position for sequentiallypositioning its respective slave switch so as to reestablish potentialbalance of the junction points of each network and correspondence of thepositions of all said switches.

4. A system for maintaining correspondence of positions of an externallypositionable master switch and a plurality of internally positionableslave switches, each of said switches having 2 +p discrete positions,where n is a positive integer including zero and p is an integersatisfying the relation 1- -1262, comprising in combination means forapplying first and second input voltages between a point of referencepotential and respectively a first and second input terminal; n+1control circuit means connected from said first input terminalrespectively to n+1 first circuit junction points; one group associatedwith each one of said slave switches, of n+1 slave switch controlnetworks connected from said second input terminal respectively to saidn+1 first circult junction points, each of said networks provided with asecond circuit junction point located in balanced relation to the firstcircuit junction point of its network relative to said point ofreference potential; auxiliary switching means for placing with thetraverse of said master switch at a first of two possible potentialsdistinct 2 +p combinations of 0, l, 2, n, n+1 of said first circuitjunction points at a time and the remaining of said first circuitjunction points at the second possible potential; one auxiliaryswitching means connected to each one of said slave switches for placingwith the traverse of its associated switch at a first of two possiblepotentials balanced normally with the aforesaid first potential relativeto said reference potential the respectively corresponding 2+p.combinations of 0, 1, 2, n, n+1, of the second circuit junctionpoints of its associated group at a time and the remaining secondcircuit junction points of such group at the second possible potentialbalanced normally with the aforesaid second potential relative to saidreference potential; and one means associated with each one of saidslave switches and responsive to unbalance of potential of the circuitjunction points of at least one network in its associated iii group dueto changed position of the master switch for sequentially positioningthe associated slave switch so as to reestablish potential balance forthe junction points of each network of such group and correspondence thepositions of all said switches.

5. A system for maintaining correspondence of positions of a first and asecond externally and internally positionable switch each having 2 +pdiscrete positions, where n is a positive integer including zero and pis an integer satisfying the relation l p 2 comprising in combinationmeans for applying first and second input voltages between a point ofreference potential and respectively a first and second input terminal;n+1 control networks connected across said input terminals each providedwith first and second circuit junction point located in balancedrelation to one another relative to said point of reference potential;auxiliary switching means for placing with the traverse of said firstswitch at a first of two possible potentials distinct 2 +p combinationsof 0, 1, 2, n, n+1 of said first circuit junction points at a time andthe remaining of said first circuit junction points at the secondpossible potential; auxiliary switching means for placing with thetraverse of said second switch at a first of two possible potentialsbalanced normally with the aforesaid first potential relative to saidreference potential the respectively corresponding 2 +p combinations of0, 1, 2, n, n+1 of said second circuit junction points at a time and theremaining second circuit junction points at the second possiblepotential balanced normally with the aforesaid second potential relativeto said reference potential; means responsive to unbalance of potentialof the circuit junction points of at least one of said networks due toexternal positioning of one of said switches for sequentially internallypositioning the other of said switches so as to reestablish potentialbalance of the circuit junction points of each of said networks andcorrespondence of switch positions; and means for precluding internalpositioning of said one externally positioned switch for a predeterminedlength of time.

6. A system for maintaining correspondence of positions of a first and asecond externally and internally positionable switch each having 2 +pdiscrete positions, where n is a positive integer including Zero and pis an integer satisfying the relation l p 2 comprising in combinationmeans for applying first and second input voltages between a point ofreference potential'and respectively a first and second input terminal;n+1 control networks connected across said input terminals each providedwith first and second circuit junction point located in balancedrelation to one another relative to said point of reference potential;auxiliary switching means for placing with the traverse of said firstswitch at a first of two possible potentials distinct 2 +p combinationsof 0, 1, 2, n, n+1 of said first circuit junction points at a time andthe remaining of said first circuit junction points at the secondpossible potential; auxiliary switching means, for placing with thetraverse of said second switch at'a first of two possible potentialsbalanced normally with the aforesaid first potential relative to saidreference potential the respectively corresponding 2 +p combinations of0, l, 2, n, n+1 of said second circuit junction points 'at a time andthe remaining second circuit junction points at the second possiblepotential balanced normally with the aforesaid second potential relativeto said reference potential; one means associated with each one of saidswitches and responsive to unbalance of potential of the circuitjunction points of at least one of said jnetworks due to externalpositioning of the other of said switches for sequentially internallypositioning its associated switch so as to reestablish potential balanceof the circuit junction points of each of said networks andcorrespondence of switch positions; and one means associated with eachone of said-switches for disabling for a predetermined 29 length of timethe operation of its associated sequential positioning means uponexternal operation of its associated switch. 7

7. A system for maintaining correspondence of positions of a first andsecond switch each having 2 +p discrete positions, where n is a positiveinteger including zero respectively a first and second input terminaltfin+1 conprising in combination means for applying first and second inputvoltages between a point of reference potential and respectively a firstand second input terminal; n+1 control networks connected across saidinput terminals each provided in order from said first to said secondinput terminal with a first outer, an intermediate and a second outercircuit junction point, the intermediate junction points of each networkbeing normally at said reference potential and the outer junction pointsof each network being located in balanced relation to one anotherrelative to said point of reference potential; auxiliary switching meansfor placing with the traverse of said first switch at a first of twopossible potentials distinct 2 combinations of 0, l, 2, n, n+1 of saidfirst outer circuit junction points at a time and the remaining of saidfirst outer circuit junction points at the second possible potential;auxiliary switching means for placing with the traverse of said secondswitch at a first of two possible potentials balanced normally with theaforesaid first potential relative to said reference potential therespectively corresponding 2 +p combinations of 0, l, 2, n, n+1 of saidsecond outer circuit junction points at a time and the remaining of saidsecond outer circuit junction points at the second possible potentialbalanced normally with the aforesaid second potential relative to saidreference potential; and means responsive to non-reference potential ofat least one of said intermediate circuit junction points due tonon-correspondence of switch positions for sequentially positioning oneof said switches so as to reestablish refrence potential at each of saidintermediate circuit junction points and correspondence of switchpositions.

8. A system for maintaining correspondence of positions of an externallypositionable master switch and an internally positionable slave switcheach having 2 +p discrete positions, where n is a positive integerincluding zero and p is an integer satisfying the relation 15 762,comprising in combination means for applying first and second inputvoltages between a point of reference potential and respectively a firstand second input terminal; n+1 control networks connected across saidinput terminals each provided in order from said first to said secondinput terminal with a first outer, an intermediate and a second outercircuit junction point, the intermediate junction point of each networkbeing normally at said reference potential and the outer junction pointsof each network being located in balanced relation to one anotherrelative to said point of reference potential; auxiliary switching meansfor placing with the traverse of said master switch at a first of twopossible potentials distinct 2 +p combinations of 0, l, 2, n, n+1 ofsaid first outer circuit junction points at a time and the remaining ofsaid first outer circuit junction points at the second possiblepotential; auxiliary switching means for placing with the traverse ofsaid slave switch at a first of two possible potentials balancednormally with the aforesaid first potential relative to said referencepotential the respectively corresponding 2 +p combinations of 0, l, 2,n, n+1 of said second outer circuit junction points at a time and theremaining of said second outer circuit junction points at the secondpossible potential balanced normally with the aforesaid second potentialrelative to said reference potential; and means responsive tonon-reference potential of at least one of said intermediate circuitjunction points due to change of master switch position for sequentiallypositioning said slave switch so as to reestablish reference potentialat each of said intermediate circuit junction points and correspondenceof switch positions.

9. A system for maintaining correspondence of posi- 2i. tions of anexternally positionable master switch and a plurality of internallypositionable slave switches, each of said switches having 2 +p discretepositions, where n is a positive integer including zero and p is aninteger satisfying the relation l p 2 comprising in combination meansfor applying first and second input voltages between a point ofreference potential and respectively a first and second input terminal;n+1 control networks connected across said input terminals each providedin order from said first to said second input terminal with a firstouter, an intermediate and a second outer circuit junction point, theintermediate junction points of each network being normally at saidreference potential and the outer junction points of each network beinglocated in balanced relation to one another relative to said point ofreference potential; auxiliary switching means for placing with thetraverse of said master switch at a first of two possible potentialsdistinct 2 +p combinations of 0, 1, 2, n, n+1 of said first outercircuit junction points at a time and the remaining of said first outercircuit junction points at the second possible potential; auxiliaryswitching means for placing with the traverse of one of said slaveswitches at a first of two possible potentials balanced normally withthe aforesaid first potential relative to said reference potential therespectively corresponding 2 +p combinations of 0, 1, 2, n, n+1 of saidsecond outer circuit junction points at a time and the remaining of saidsecond outer circuit junction points at the second possible potentialbalanced normally with the aforesaid second potential relative to saidreference potential; and a means associated with each of said slaveswitches responsive to non-reference potential of at least one of saidintermediate circuit junction points due to change of master switchposition for sequentially positioning its respective slave switch so asto reestablish reference potential at each of said intermediate circuitjunction points and correspondence of positions of all of said switches.

10. A system for maintaining correspondence of positions of anexternally positionable master switch and a plurality of internallypositionable slave switches, each of said switches having 2 +p discretepositions, where n is a positive integer including zero and p is aninteger satisfying the relation l p 2 comprising in combination meansfor applying first and second input voltages 'between a point ofreference potential and respectively a first and second input terminal;n+1 control circuit means connected from said first input terminalrespectively to n+1 first outer circuit junction points; one groupassociated with each one of said slave switches, of n+1 control networksconnected from said second input terminal respectively to said n+l outercircuit junction points, each of said networks provided in order fromits respective first outer circuit junction point to said second inputterminal with an intermediate and a second outer circuit junction point,the intermediate junction points of each network being normally at saidreference potential and the outer junction points of each network beinglocated in balanced relation to one another relative to said point ofreference potential; auxiliary switching means for placing with thetraverse of said master switch at a first of two possible potentialsdistinct 2 +p combinations of 0, l, 2, n, n+1 of said first outercircuit junction points at a time and the remaining of said first outercircuit junction points at the second possible potential; one auxiliaryswitching means connected to each one of said slave switches for placingwith the traverse of its associated switch at a first of two possiblepotentials balanced normally with the aforesaid first potential relativeto said reference potential the respectively corresponding 2 '+pcombinations of 0, l, 2, n, n+1 of the second outer circuit junctionpoints of its associated group at a time and the remaining second outercircuit junction points of such group at the second possible potentiala1 ced normally with the aforesaid second potential relative to saidreference potential; and one means associated with each one of saidslave switches and responsive to non-reference potential of at least oneintermediate circuit junction point in its associated group due tochange of master switch position for sequentially positioning itsrespective slave switch so as to re-establish reference potential ateach of said intermediate circuit junction points of such group andcorrespondence of the positions of all said switches.

11. A system for maintaining correspondence of positions of a first anda second externally and internally positionable switch each having 2 +pdiscrete positions, where n is a positive integer including zero and pis an integer satisfying the relation l p 2 comprising in combinationmeans for applying first and second input ;s between a point ofreference potential and reop uvely a first and second input terminal;n+1 control networks connected across said input terminals each proaidedin order from said first to said second input terminal with a firstouter, an intermediate and a second outer circuit junction point, theintermediate junction points of each network being normally at saidreference potential and the outer junction points of each network beinglocated in balanced relation to one another relative to said point ofreference potential; auxiliary switching means for placing with thetraverse of said first switch at a first of two possible potentialsdistinct 2 +p combinations of O, 1, 2, n, n+1 of said first o tcrcircuit junction points at a time and the remaining of said first outercircuit junction points at the second possible potential; auxiliaryswitching means for placing with the traverse of said second switch at afirst of two possible potentials balanced normally with the aforesaidfirst potential relative to said reference potential the respectivelycorresponding 2 +p combinations of O, l, 2,

. n, n+1 of said second outer circuit junction points at a time and theremaining of said second outer circuit junction points at the secondpossible potential balanced normally with the aforesaid second potentialrelative to said reference potential; and means responsive tonon-reference potential of at least one of said intermediate circultjunction points due to external positioning of one of said switches forsequentially internally positioning the other of said switches so as toreestablish reference potential at each of said intermediate circuitjunction points and correspondence of switch positions; and means forprecluding internal positioning of said one externally positioned switchfor a predetermined length of time.

12. A system for maintaining correspondence of positrons of a first anda second externally and internally positionable switch each having 2 +pdiscrete positions, where n is a positive integer including zero and pis an integer satisfying the relation l p 2 comprising in combinationmeans for applying first and second input voltages between a point ofreference potential and respectively a first and second input terminal;n+1 control networks connected across said input terminals each providedin order from said first to said second input terminal with a firstouter, an intermediate and a second outer circuit junction point, theintermediate junction points of each network being normally at saidreference potential and the outer junction points of each network beinglocated in balanced relation to one another relative to said point ofreference potential; auxiliary switching means for placing with thetraverse of said first switch at a first of two possible potentialsdistinct 2 +p cornbinations of O, 1, 2, n, n+1 of said first outercircuit junction points at a time and the remaining of said first outercircuit junction points at the second possible potential; auxiliaryswitching means for placing with the traverse of said second switch at afirst of two possible potentials balanced normally with the aforesaidfirst potential relative to said reference potential the respectivelycorresponding 2 +p combinations of 0, l, 2,

n, n+1 of said second outer circuit junction points at a time and theremaining of said second outer circuit junction points at the secondpossible potential balanced normally with the aforesaid second potentialrelative to said reference potential; one means associated with each oneof said switches and responsive to non-reference potential of at leastone of said intermediate junction points due to external positioning ofthe other of said switches for sequentially internally positioning itsassociated switch so as to reestablish reference potential of each ofsaid inter mediate junction points and correspondence of switch positions; and one means associated with each one of said switches fordisabling for a predetermined length of time the operation of itsassociated sequential positioning means upon external operation of itsassociated switch.

13. A system for maintaining correspondence of positions of a first andsecond switch each having 2 +p discrete positions, Where n is a positiveinteger including zero and p is an integer satisfying the relation 1 ,72, comprising in combination means for applying first and secondbalanced alternating input voltages betweeh a point of referencepotential and respectively a first and second input terminal; n+1resistive control networks connected across said intput terminals eachprovided in order from said first to said second input terminal with afirst outer, an intermediate and a second outer circuit junction point,the intermediate junction points of each network being normally at saidreference potential and the outer junction points of each network beinglocated in balanced relation to one another relative to said point ofreference potential; n+1 rectifiers having one set of like electrodesconnected respectively to said intermediate circuit junction points andhaving the other like electrodes connected together to a rectifier loadterminal; a rectifier load network connected from said rectifier loadterminal to said point of reference potential; auxiliary switching meansfor placing with the traverse of said first switch at a first of twopossible potentials distinct 2 +p combinations of 0, l, 2, n, n+1 ofsaid first outer circuit junction points at a time and for placing theremaining of said first outer circuit junction points at the secondpossible potential; auxiliaryswitching means for placing with thetraverse of said second switch at a first of two possible potentialsbalanced normally with respect to the aforesaid first potential therespectively corresponding 2 combinations of 0, 1, 2, n, n+1 of saidsecond outer circuit junction points at a time and for placing theremaining of said second outer circuit junction points at the secondpossible potential balanced normally with respect to the aforesaidsecond potential; and means responsive to the flow of a rectifiedunbalance current from at least one of said intermediate circuitjunction points through said rectifier load network due tononco-rrespondence of switch positions for sequentially positioning oneof said switches so as to restore reference potential at each of saidintermediate circuit junction points and correspondence of switchpositions.

14. A system for maintaining correspondence of positions of anexternally positionable master switch and an internally positionableslave switch each having 2 +p discrete positions, where n is a positiveinteger including zero and p is an integer satisfying the relation 16952, comprising in combination means for applying first and secondbalanced alternating input voltages between a point of referencepotential and respectively a first and second input terminal; n+1resistive control networks connected across said input terminals eachprovided in order from said first to said second input terminal with afirst outer, an intermediate and a second outer circuit one set "of likeelectrodes connected respectively to said intermediate circuit junctionpoints and having the other like electrodes connected together to arectifier load terminal; a rectifier load network connected from saidrectifier load terminal to said point of reference potential; auxiliaryswitching means for placing with thetraverse of said master switch at afirst of two possible potentials distinct 2 combinations of 0, 1, 2, n,n+1 of said first outer circuit junction points at a time and forplacing the remaining of said first outer circuit junction points at thesecond possible potential; auxiliary switching means for placing-withthe traverse of. said slave switch at a first of two possible potentialsbalanced normally with respect to the aforesaid first po tential therespectively corresponding 2 +p combinations of 0, l, 2, 'n, n+1 of saidsecond outer'circuit junction points at a "time and for placing theremaining of said second outer circuit junction points at the secondpossible potential balanced normally with respect to the aforesaidsecond potential; and means responsive to the flow of a rectifiedunbalance 'currentfrom at least one of said intermediate circuitjunction points throughsa'id rectifier load network due to change inmaster switch position for sequentially positioning said slave switch soas'to restore reference potential at each of said intermediate circuitjunction points and correspondence of switch positions.

15. A system for maintaining correspondence of positions of anexternally positionable master switch and a plurality of internallypositionable slave switches, each of said switches having 2 +p discretepositions, where n is a positive integer including zero and p is aninteger satisfying the relation I p Z comprising in combination meansfor applying first and second balanced alternating input voltagesbetween a point of reference potential and respectively a first andsecond input terminal; n+1 resistive control networks connected acrosssaid input terminals each provided in order from said first to saidsecond input terminal with a first outer an intermediate and a secondouter circuit junction point, the intermediate junction points of eachnetwork being normally at said reference potential and the outerjunction points of each network being located in balanced relation toone another relative to said point of reference potential; n+1rectifiers having one set of like electrodes connected respectively tosaid intermediate circuit junction points and having the other likeelectrodes connected together to a rectifier load terminal; a rectifierload net- Work'connected from said rectifier load terminal to said pointof reference potential; auxiliary switching means for placing with thetraverse of said master switch at a first of two possible potentialsdistinct 2 +p combinations of 0, 1, 2, n, n+1 of said first outercircuit junction points at a time and for placing the remaining of saidfirst outer circuit junction points at the second possible potential;auxiliary switching means for placing with the traverse of one of saidslave switches at a first of two possible potentials balanced normallywith respect to the aforesaid first potential the respectivelycorresponding 2 +p combinations of 0, 1, 2, n, n+1 of said second outerjunction points at a time and for placing the remaining of said secondouter circuit junction points at the second possible potential balancednormally with respect to the aforesaid second potential;

' and a means associated with each one of saidslave switches andresponsive to the flow of a rectified unbalance current from at leastone of said intermediate circuit junction points through said rectifierload network due to change in master switch position for sequentiallypositioning its respective slave switch so as to restore referencepotential at each of said intermediate circuit junction points andcorrespondence of the positions of all said switches.

16. A system for maintaining correspondence of positions of anexternally positionable master switch and assaras a plurality ofinternally positionable slave switches, each of said switches having2"|p discrete positions, Where n is a positive integer including zeroand pis an integer satisfying the relation 1 19 2", comprising incombination means for applying first and second balanced alternatinginput voltages between a point of reference potential and respectively afirst and second input terminal; n+1 resistors connected from said firstinput terminal respectively to n+1 first outer circuit junction points;one group associated with each one of said slave switches, of n+1resistive control networks connected from said second input terminals torespectively said n+1 first outer circuit junction points, each of saidnetworks provided in order from its respective first outer circuitjunction point to said second input terminal with an intermediate and asecond outer circuit junction point, the intermediate junction points ofeach network being normally at said reference potential and the outerjunction points of each network being located in balanced relation toone another relative to said point of reference potentials; n+1rectifiers associated with each of said groups having one set of likeelectrodes connected respectively to said intermediate circuit junctionpoints of the associated group and having the other like terminals ineach group connected together to a rectifier load terminal associatedwith such group; a rectifier load network for each of said groupsconnected from the associated rectifier load terminal to said point ofreference potential; auxiliary switching means for placing with thetraverse of said master switch at a first of two possible potentialsdistinct 2 +p combinations of 0, 1, 2, n, n+1 of said first outercircuit junction points at a time and for placing the remaining of saidfirst outer circuit junction points at the second possible potential;one auxiliary switching means connected to each one of said slaveswitches for placing with the traverse of its associated slave switch ata first of two possible potentials balanced normally with respect to theaforesaid first potential the respectively corresponding 2 +pcombinations of O, 1, 2, n, n+1 of the second outer circuit junctionpoints of its associated group at a time and for placing the remainingof the second outer circuit junction points of its associated group atthe second possible potential balanced normally with respect to theaforesaid second potential; and one means associated with each one ofsaid slave switches and responsive to the flow of a rectified unbalancecurrent from at least one of the intermediate circuit junction points ofits associated group through the associated rectifier load network dueto change in master switch position for sequentially positioning itsrespective slave switch so as to restore reference potential at each ofthe associated intermediate circuit junction points and correspondenceof the positions of all said switches.

17. A system for maintaining correspondence of positioning of a firstand a second externally and internally positionable switch each having 2discrete positions, where n is a positive integer including zero and pis an integer satisfying the relation I p Z, comprising in combinationmeans for applying first and second balanced alternating input voltagesbetween a point of reference potential and respectively a first andsecond input terminal; n+1 resistive control networks connected acrosssaid input terminals each provided in order from said second inputterminal with a first outer, an intermediate and a second outer circuitjunction point, the intermediate junction points of each network beingnormally at said reference potential and the outer junction points ofeach network being located in balanced relation to one another relativeto said point of reference potential; n+1 rectifiers having one set oflike terminals connected respectively to said intermediate circuitjunction points and having the other like electrodes connected togetherto a rectifier load terminal; a rectifier load network connected fromsaid rectifier load terminal to said point of reference potential;auxiliary switching means for placing with the traverse of said firstswitch at a first of two possible potentials distinct 2"+p combinationsof 0, 1, 2, n, n+1 of said first outer circuit junction points at a timeand for placing the remaining of said first outer junction points at thesecond possible potential; auxiliary switching means for placing withthe traverse of said second switch at a first of two possible potentialsbalanced normally with respect to the aforesaid first potential therespectively corresponding 2"|p combinations of 0, 1, 2, n, n+1 of saidsecond outer circuit junction points at a time and for placing theremaining of said second outer circuit junction points at the secondpossible potential balanced normally with respect to the aforesaidsecond potential; means responsive to the flow of a rectified unbalancecurrent from at least one of said intermediate circuit junction pointsthrough said rectifier load network due to external positioning of oneof said switches for sequentially internally positioning the other ofsaid switches so as to restore reference potential at each of saidintermediate circuit junction points and correspondence of switchpositions; and means for precluding internal positioning of said oneexternally positioned switch for a predetermined length of time.

18. A system for maintaining correspondence of positions of a first anda second externally and internally positionable switch each having 2 +pdiscrete positions, where n is a positive integer including Zero and pis an integer satisfying the relation 16 2 2, comprising in combinationmeans for applying first and second balanced alternating input voltagesbetween a point of reference potential and respectively a first andsecond input terminal; n+1 resistive control networks connected acrosssaid input terminals each provided in order from said first to saidsecond input terminal with a first outer, an intermediate and a secondouter circuit junction point, the intermediate junction points of eachnetwork being normally at said reference potential and the outerjunction points of each network being located in balanced relation toone another relative to said point of reference potential; n+1rectifiers having one set of like terminals connected respectively tosaid intermediate circuit junction points and having the other likeelectrodes connected together to a rectifier load terminal; a rectifierload network connected from said rectifier load terminal to said pointof reference potential; auxiliary switching means for placing with thetraverse of said first switch at a first of two possible potentialsdistinct 2 +p combinations of 0, 1, 2, n, n+1 of said first outercircuit junction points at a time and for placing the remaining of saidfirst outer junction points at the second possible potential; auxiliaryswitching means for placing with the traverse of said second switch at afirst of two possible potentials balanced normally with respect to theaforesaid first potential the respectively corresponding 2 +pcombinations of O, 1, 2, n, n+1 of said second outer circuit junctionpoints at a time and for placing the remaining of said second outercircuit junction points at the second possible potential balancednormally with respect to the aforesaid second potential; one meansassociated with each one of said switches and responsive to the flow ofa rectified unbalance current from at least one of said intermediatecircuit junction points due to external positioning of the other of saidswitches for sequentially internally positioning its associated switchso as to restore reference potential at each of said intermediatecircuit junction points and correspondence of switch positions; and onemeans associated with each one of said switches for disabling for apredetermined length of time the operation of its associated sequentialpositioning means upon external operation of its associated switch.

19. The combination as defined in claim 1, wherein a switch ispositionable externally bidirectionally and internally unidirectionally.

20. The combination as defined in claim 6 wherein the sequentialpositioning means of one switch is operable unidirectionally and isconnected to its associated one switch, and wherein the disabling meansincludes means for disconnecting for the predetermined length of timesaid sequential positioning means from said one switch responsive toexternal operation of said one switch, thereby to permit externaloperation of said one switch in either direction.

21. The combination as defined in claim 6 wherein the sequentialpositioning means of one switch comprises a rotary solenoid having arotor and being energizable responsive to external operation of theother switch, and wherein the disabling means is effective to open forthe predetermined length of time the energizing circuit for said rotarysolenoid responsive to external positioning of said one switch.

22. The combination as defined in claim 21 wherein the rotary solenoidis operable internally unidirectionally, wherein its rotor is connectedto its associated one switch and wherein the disabling means includesmeans for disconnecting for the predetermined length of time said rotorfrom said one switch responsive to external operation of said oneswitch, thereby to permit external operation of said one switch ineither direction.

23. The combination as defined in claim 6 wherein the sequentialpositioning means of one switch comprises a rotary solenoid energizableresponsive to unbalance of potential of the circuit junction points ofat least one of the networks due to external positioning of the otherswitch, and wherein the disabling means is effective to open for thepredetermined length of time the energizing circuit for said rotarysolenoid responsive to external positioning of said one switch.

24. The combination as defined in claim 12 wherein the sequentialpositioning means of one switch comprises a rotary solenoid energizableresponsive to non-reference potential of at least one of theintermediate junction points due to external positioning of the otherswitch, and wherein the disabling means is effective to open for thepredetermined length of time the energizing circuit for said rotarysolenoid responsive to external positioning of said one switch.

25. The combination as defined in claim 18 wherein the sequentialpositioning means of one switch comprises a rotary solenoid energizableresponsive to the flow of a rectified unbalance current through therectifier load network due to external operation of the other switch,and wherein the disabling means is elfective to open for thepredetermined length of time the energizing circuit for said rotarysolenoid responsive to external positioning of said one switch.

26. The combination as defined in claim 24 wherein the rotary solenoidhas a rotor connected to its associated one switch, and wherein thedisabling means includes means also responsive to non-referencepotential of at least one or" the intermediate junction points fordisconnecting said rotor from its associated one switch for thepredetermined length of time, thereby to permit external operation ofsaid one switch in either direction.

27. The combination as defined in claim 25 wherein the rotary solenoidhas a rotor connected to its associated one switch, and wherein thedisabling means in? cludes means also responsive to the flow of arectified unbalance current through the rectifier load network fordisconnecting said rotor from its associated one switch for thepredetermined length of time, thereby to permit external operation ofsaid one switch in either direction.

References (Zited in the file of this patent UNITED STATES PATENTS

